In diverse cell types such as muscle, fibroblasts and bone, the cells can generate contractile or traction forces while being responsive to electrophysiological and mechanical signals. Although subsets of these interactions have been studied under the themes of mechanotransduction and excitation-contraction coupling, a full understanding of the interrelationship between cell mechanics and cell electrophysiology requires the simultaneous measurement of cell force, cell voltage and cell current during the application of external forces. The goal of this project is to assemble, for the first time, an integrated measurement and force application system that will enable the functional role of mechanosensitive channels, transmembrane voltage, and specific membrane currents to be examined in cells having different cytoskeletal architectures. The model system that will be studied is the cardiac myofibroblast, a cell that plays a prominent role in myocardial infarcts and scar formation and is capable of force sensing, force production, and electrophysiological activity. In recent years, micropatterned flexible substrates, such as arrays of elastomeric micrometer-scale posts that deflect under cellular traction forces have emerged as novel systems for measuring cellular contractility with sub-cellular resolution. Further, by embedding magnetic nanoparticles in some of the posts, it is now possible to apply forces to adherent cells while measuring their mechanical responses via the surrounding non-magnetic posts. In this project, magnetic micropost-based force generation and measurement systems will be combined with electrophysiological techniques to enable simultaneous electrical and mechanical stimulation and readout of single cells. This project will be a joint effort between the laboratories of two Investigators with complementary expertise in cardiac electrophysiology, experimental physics, patterned cell growth, magnetism, microfabrication, and cell mechanics. Specific Aim 1 will integrate single cell traction force measurements via the micropost arrays with electrophysiological measurements of transmembrane potential and membrane ionic currents. Micro contact printing will be used to vary the shape of the myofibroblasts to manipulate their internal distribution of actin stress fibers, and to explore the effect of sub-cellular force distributions on transmembrane potential and currents. Specific Aim 2 will integrate magnetic actuation of mechanical forces and strains into the electromechanical readout system developed in Aim 1, and will study the mutual interactions of cellular mechanical and electrophysiological responses to external force and strain. By creating a unified technology for the study of cellular mechanoelectrical function, this project will open new directions for the elucidation of biologically and clinically important systems. )